Accessing data and updating data in a plugin


I have a plugin that displays data in a Gantt view.

I can pass simple data into the Plugin using Fields but that is quite limiting. What I want to be able to do is look up data in the database using something similar to “Do a search for” so I can retrieve related records and change the display of the bars in the Gantt.

Is this possible? How would I go about it? Are there any good examples?

In the Plugin editor, I can see the API Calls section but I am not sure what/how to use these calls. Is there an example of how to use the API Calls once they are set up?

Thanks in advance.